The mouse promoter drives B cell-specific expression of the human MYC coding sequence (exons 2 and 3; Genbank vector). A codon mutation generates a STOP codon at the third codon (TCG to TAG) and prevents expression of MYC. The codon substitution created a DGYW motif, a known preferential target sequence for somatic hypermutation, that can activate MYC translation following sporadic reversion. This vector lacks the loxP site found in Tg(Igkv3-5*-MYC)24Plbe. Line 4 inserted at chr14:74838906-74848613 (mm39) with deletion of intervening region. (J:94077, J:131912)